D1‐dopamine receptor agonists increase phrenic nerve activity and synchronization with renal sympathetic nerve discharges in the adult rat in vivo

Abstract

In adult cats in vivo, D1-dopamine receptor (D1R) agonists increase phrenic nerve discharge (PND) intensity and PND sensitivity to CO2. Our goals in the present investigation were to: One, determine if a highly selective D1R agonist, SKF 38393 (SKF), affects PND in the rat. Two, determine if SKF affects synchronization between PND and renal sympathetic nerve discharges (RSND). We performed experiments on anesthetized, vagotomized, paralyzed and mechanically ventilated adult rats. We gave SKF i.v. in graded doses and recorded raw and integrated PND and RSND, arterial blood pressure, end-tidal CO2 and rectal temperature. We also cross-correlated PND (as source) and RSND (destination). We observed two principal SKF effects: PND intensity increased after doses of 0.25–2 mg/kg without change in discharges/minute. Peak intensity increased 32.6 ± 3.9% (mean ± SE) at 1 mg/kg and reached a plateau or declined with larger (3–4 mg/kg) doses. RSND exhibited a rhythm synchronized to PND after all test doses of SKF, increasing in parallel with PND intensity. We suggest that SKF stimulates a common source of excitation and coupling between central respiratory and sympathetic motor outputs.